[Extensions] Fix improper extension tab ownership bug

extensions/common/extension_messages.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // IPC messages for extensions.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <vector>
 
@@ skipping 409 matching lines @@
 IPC_MESSAGE_CONTROL2(ExtensionMsg_SetSystemFont,
                      std::string /* font_family */,
                      std::string /* font_size */)
 
 // Marks an extension as 'active' in an extension process. 'Active' extensions
 // have more privileges than other extension content that might end up running
 // in the process (e.g. because of iframes or content scripts).
 IPC_MESSAGE_CONTROL1(ExtensionMsg_ActivateExtension,
                      std::string /* extension_id */)
 
-// Notifies the renderer that the current tab is an extension page (we limit
-// what other extensions can do on these pages).
-IPC_MESSAGE_ROUTED1(ExtensionMsg_SetMainFrameExtensionOwner,
-                    std::string /* extension_id */)
-
 // Notifies the renderer that extensions were loaded in the browser.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_Loaded,
                      std::vector<ExtensionMsg_Loaded_Params>)
 
 // Notifies the renderer that an extension was unloaded in the browser.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_Unloaded,
                      std::string)
 
 // Updates the scripting whitelist for extensions in the render process. This is
 // only used for testing.
@@ skipping 343 matching lines @@
                     int /* acc_obj_id */,
                     base::string16 /* selector */)
 
 // Result of a query selector request.
 // result_acc_obj_id is the accessibility tree ID of the result element; 0
 // indicates no result.
 IPC_MESSAGE_ROUTED3(ExtensionHostMsg_AutomationQuerySelector_Result,
                     int /* request_id */,
                     ExtensionHostMsg_AutomationQuerySelector_Error /* error */,
                     int /* result_acc_obj_id */)